Method and apparatus for monitoring wall thickness of blow-molded plastic containers

ABSTRACT

A method of inspecting wall thickness of blow-molded plastic containers includes providing a blow-molder having a plurality of molds and a plurality of associated spindles. The containers are inspected by impinging infrared light thereon and detecting the portion of the infrared light that passes through the container and converting the same into corresponding electrical signals which are delivered to a microprocessor. The microprocessor compares the electrical signals with stored information regarding desired wall thickness of the container and emits output thickness information. The microprocessor receives signals from sensors associated with the blow-molder relating to the position of the molds, the identity of the molds and the identity of the spindles in order that the wall thickness information that is determined by inspection can be associated with specific molds and spindles. The wall thickness information may be averaged over a period of time or a number of containers. The information may be visually displayed so as to provide feedback regarding the inspection process. In a preferred embodiment wall thickness measurements are taken at several vertically spaced positions simultaneously. Corresponding apparatus is provided.

This application is a continuation of U.S. patent application Ser. No.10/106,263, filed 3/26/2002, now U.S. Pat. No. 6,863,860.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention provides an automated on-line method and apparatusfor inspecting wall thickness of blow-molded plastic containers and,more specifically, it provides feedback regarding the thicknessmeasurements such that the particular container being inspected isassociated with a specific mold and spindle.

2. Description of the Prior Art

It has long been known that plastic containers such as bottles must beinspected in order to make sure that the wall thickness is adequate forthe desired purpose and that the use of excess material is minimized.

In general, it has been known to employ sampling inspection techniqueswherein, at a periodic intervals, which might be on the order of onceper hour, a container was removed from the conveyance system after thecontainer emerged from the blow-molder and was destructively tested bycutting the same into multiple, horizontal sections which were thenweighed with the weight being correlated with the wall thickness.

An alternative inspection method involved measuring the wall thicknessof such containers by nondestructively testing sample plasticcontainers. A suitable system for effecting such testing is the AGR TopWave Profiler Gauge PG 9800. A suitable laboratory instrument for thislatter approach is that sold under the trademark AGR Top Wave WallThickness Profiler. One of the problems with such an inspection approachis that it was time-consuming and labor intensive. Also, the longinterval between samplings resulted in a delay in process feedback whichin turn could result in reduced production efficiencies.

It has also been known to employ high-speed on-line wall thicknessmonitoring systems for blow-molded plastic containers. These systemsprovide real-time monitoring of material distributions and rejection ofdefects. A suitable system for such purpose is that sold under thetrademark AGR Top Wave PET Wall System. While these systems represent asubstantial improvement in the completeness of sampling by inspectingeach container and the timing of same, they did not provide feedbackcoordinated with the operation of the blow-molding machine.

U.S. Pat. No. 4,304,995 discloses a system for measuring wall thicknessof plastic containers employing infrared absorption. The containers aresampled off-line and required the use of rotation and disclosed the useof radiation sources and radiation detectors which were structured torotate with respect to each other.

U.S. Pat. No. 4,490,612 discloses a method of measuring the thickness ofplastic film using relative absorptions of two infrared wavelengths.

U.S. Pat. No. 5,139,406 discloses the use of infrared absorption inmeasuring the wall thickness of plastic containers. On-line measurementis contemplated, but this system requires insertion of a probe into thecontainer. Such an approach is uneconomical and inefficient in respectof current blow-molder plastic container production speeds.

U.S. Pat. No. 5,591,462 discloses the use of machine vision technologyin monitoring certain defects in blow-molded containers. Among thefeatures being monitored by this system are seal surface, base and neckfolds and finish gauge inspection.

PCT publication WO 01/65204 discloses a method and apparatus formeasuring plastic containers on-line employing infrared absorption. Theapparatus was said to be employable on a conveyer or inside theblow-molder. It made use of laterally homogenous material distributionproperties and measured though both sides of the container.

In spite of the foregoing prior art disclosures, there remains a veryreal and substantial need for an improved inspection system for blowmolded plastic containers which will provide timely and accuratefeedback regarding not only whether a container fell within the wallthickness specifications, but also identity of the molds and associatedspindles which produced the container.

SUMMARY OF THE INVENTION

The present invention has met the above-described need.

The method of the present inventions involves inspection of the wallthickness of blow-molded plastic containers by providing a plasticcontainer blow-molder having a plurality of molds and a plurality ofassociated spindles. The containers are inspected by impinging infraredlight thereon and detecting the portion of the infrared light thatpasses though the container and converting the same to correspondingelectrical signals which are delivered to a microprocessor. Themicroprocessor receives the thickness related signals and compares themwith stored information regarding the desired thickness and emitsthickness information. A visual display of such information, which mayinclude an average container wall thickness over a period of time, foreach mold and spindle may be provided.

The method may involve providing a plurality of such systems so thatcontainer wall thickness may be measured substantially simultaneously ata plurality of elevations.

The method includes sensing a plurality of conditions in theblow-molder, including mold position, mold identity and spindle identitysuch that the thickness determined can be synchronized with a particularmold and spindle to thereby provide meaningful feedback regarding thethickness determination.

The presence of a container to be inspected in the inspection station isalso provided. A reject mechanism for physically removing a rejectedcontainer is also provided.

The apparatus of the present invention includes an inspection stationpreferably disposed inside of the blow-molder and having at least onesource of infrared radiation which impinges the radiation on the plasticcontainer to be inspected and cooperating photodetectors which may bephotoconductive lead-sulfide infrared detectors, for example. Thesereceive the infrared radiation passing through the container and convertthe same into corresponding electrical signals which are delivered tothe microprocessor. The microprocessor contains stored informationregarding the desired thickness and is structured to effect a comparisonand issue thickness information output signals which may go to a visualdisplay unit for presentation to an operator and may also, if thecontainer is to be rejected, present such a signal to the rejectmechanism which will remove the container from the line. Sensors forsensing the mold assembly position, as well as the identity of each moldand spindle so as to synchronize the same with the container beinginspected are provided and are preferably disposed within theblow-molder.

It is an object of the present invention to provide an improvedautomated on-line rapid inspection system for inspecting wall thicknessof plastic containers, such as bottles, for example.

It is another object of the invention to provide a method an apparatusfor effecting such inspection while providing meaningful feedbackregarding the specific mold and spindle which made a given container.

It is another object of the present invention to provide such a systemwhich employs sensors within the blow-molder to provide information to amicroprocessor regarding mold position and mold and spindle identity asrelated to a specific blow-molded container.

It is an object of the present invention to provide a system which isadapted for rapid on-line assembly of plastic bottles and other plasticcontainers made by blow-molding in such a manner as to identify the moldand spindle which made a specific container.

It is a further object of the present invention to provide such a systemwhich will facilitate immediate communication of wall thicknessinformation for either manual or automated control of the blow-moldingsystem.

It is a further object of the invention to provide such a system whichenhances the efficiency of the manufacture of blow-molded plasticcontainers.

These and other objects of the present invention will be more fullyunderstood from the following description of the invention on referenceto the illustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing the blow-molder, containertransporting mechanisms, the inspection area and reject area.

FIG. 2 is a perspective view showing a form of light source andassociated photodetector employable in the inspection station of thepresent invention.

FIG. 3 is a schematic diagram showing a form of apparatus usable in thepresent invention and the interaction of the same.

FIG. 4 is an algorithm flow chart illustrating the flow of informationin an embodiment of the present invention.

FIGS. 5( a), (b) and (c) illustrate a timing diagram showing therelationship among machine step, mold sync and spindle sync signals.

FIG. 6 illustrates a screen of a visual display unit employable in thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “containers” refers to plastic bottles,jars, vials and other plastic containers usable for storage of liquidand other flowable materials. Examples of the size of containers forwhich the present invention is particularly well suited are containershaving a capacity of about 0.2 to 3 liters.

In a typical prior art plastic container, blow-molding process preformsentering the blow-molder are typically at room temperature. The preformsare inverted and loaded, upside-down, onto spindles. The spindles carrythe preforms through the reheat oven which raises the temperature of theplastic in preparation for blow-molding. Uniform heating is important sothe spindles rotate as they traverse through the oven. There aretypically 100 to 400 spindles, forming a conveyor loop. After exitingthe reheat oven, the preforms are removed from the spindles andtransferred by a system of transfer wheels into the molds on the moldwheel. Failure of the spindles to rotate correctly while traversingthrough the oven will result in a poor thickness distribution in theblown container.

Employing one or more light sources of infrared radiation andcooperating associated photodetectors preferably located within theblow-molder near the output portion of a blow-molder where thecontainers are extracted from the molds, container wall thickness canreadily and rapidly be determined. It is known that plastic materialssuch as PET absorb infrared radiation of specific wavelengths. Thisfacilitates determination of the thickness of the container wall basedon the amount of infrared radiation that has been absorbed. In apreferred practice of the present invention, the thickness monitoringapparatus and method will employ two distinct infrared wavelengths inorder to compensate for refractive and scattering effects that mightotherwise have a deleterious effect on the measurement.

Referring to FIG. 1, a preform oven 2 typically carries the plasticpreforms on spindles through the oven section so as to preheat thepreforms prior to blow-molding of the containers. The preforms leavingthe preform oven 2 enter the mold assembly 6 which contains a pluralityof molds by means of conventional transfer apparatus 7 (shown inphantom). The blow-molder 4, which may be of conventional type, has thearray of molds which may be on the order of ten to twenty-four arrangedin a circle and rotating in a direction indicated by the arrow C.Containers emerging from the mold assembly 6, such as container 8, willbe suspended from a transfer arm, such as 10, on transfer assembly 12which is rotating in the direction indicated by arrow D. Similarly,transfer arms 14 and 16 will, as the transfer assembly 12 rotates, pickup a container such as 8 and transport it through the inspection area 20which will be described in greater detail hereinafter. A reject area 24has a reject mechanism 26 which will physically remove from the transferassembly 12 any containers deemed to be rejects. Container 30 has passedbeyond the reject area 24 and will be picked up in star wheel 34 whichis rotating in direction E and has a plurality of pockets, such as 36,38, 40, for example. Container 46 is shown as being present in such astar wheel pocket. The containers will then be transferred in a mannerknown to those skilled in the art to conveyer means according to thedesired transport path and nature of the system.

Referring to FIG. 2, there is shown a form of inspection station 20which has a container 60 passing therethrough in the direction indicatedby the arrow under the influence of a suitable conveyance device (notshown). In the form shown, a plurality of light sources 64, 66, 68 arevertically spaced from each other in order to inspect the wall thicknessof the bottle at three zones at three different elevations. Cooperatingwith the light sources 64, 66, 68, respectively, are photodetectors 74,76, 78. In operation, infrared radiation will be emitted by the lightsources 64, 66 68, impinge upon bottle 60, have a portion of theinfrared radiation absorbed by the plastic container 60 and have theremaining infrared radiation impinge upon the detectors 74, 76, 78 whichwill convert the received light into a corresponding electrical signalwhich will be delivered to a microprocessor for further processing. Anysuitable detector which will function efficiently with the infraredradiation wavelengths employed may be used. A preferred detector is aphotoconductive lead-sulfide (PbS) infrared detector. A suitable PbSdetector is that sold by CalSensors. In a preferred system, the detectorassembly consists of a prism-grating-prism spectrograph and two or morePbS detectors (such an assembly is manufactured by Spectral Imaging,Ltd. Of Finland, using PbS detectors from CalSensors). The spectrographdisperses the infrared radiation as a function of wavelength; thedetectors are located so as to be sensitive to specific wavelengths ofinfrared radiation. One wavelength is selected to correspond to anabsorption band in the plastic container. A second wavelength isselected to correspond to a transmission band in order to provide areference. As an alternative to using the spectrograph, band-passoptical filters may be used in conjunction with the PbS detectors.

Referring still to FIG. 2, further details regarding the creation ofsynchronized wall thickness determination as related to specific moldsand spindles will be considered. The light source preferably includes ahalogen bulb that is always on, a lens to collect and collimate thelight into a beam, a spinning segmented disk that “chops” the light beamand a remotely-controlled calibration disk. The light source ispreferably always “on,” emitting a pulsed beam (which preferably pulsesat about 600 Hz). The light source emits a pulsed beam of “white” light,containing all of the desired infrared wavelengths.

Referring to FIG. 3, there is shown a microprocessor 90 which, in theform shown, exercises control over the calibration disks, which arepreferably integral with light sources 92, 94, 96 and 98. A containerwhich will pass through the gap indicated generally as 100 will, in theform shown, receive light from sources 92, 94, 96 98, absorb a portionof the same and then have the light not absorbed impinge onphotodetector sensors 102, 104, 106 108, respectively, which willconvert the received light into corresponding electrical signals whichare delivered to the microprocessor 90.

In a preferred embodiment of the invention, three key sensors which arewithin or operatively associated with the blow molder, provideinformation to enable synchronization of the specific molds and spindleswhich made the container being inspected and thereby provide valuablefeedback information. One sensor, designated the blow-molder machinestep sensor 120, emits a signal which contains information regarding thecounting of the molds and spindles from their corresponding startingposition. The total number of molds or spindles may vary depending uponthe make and model of blow-molder, but this information is known inadvance. This information may be programmed into the system. A secondsignal, which is from the blow-molder synchronization sensor 122,provides information regarding start of a new cycle of rotating the moldassembly. The output of this sensor 122 is provided to microprocessor90. The blow-molder spindle synchronizing sensor 126 provides outputregarding the new cycle of rotating the spindle assembly. This output isprovided to the microprocessor 90. The sensors employed for monitoringmachine step mold sync and spindle sync may be positioned at anysuitable location within the blow-molder and may be of any suitabletype, such as inductive sensors which are well known to those skilled inthe art.

The part-in-place sensor 130 provides a signal to the computerindicating that a container has arrived at the inspection station andthat the wall thickness inspection should be initiated. At that point,the container transects the beams of white light containing all of thedesired infrared wavelengths emitted by light sources 92, 94, 96, 98.The system preferably employs an incandescent light bulb that isoperated in a continuous mode. This continuous light is preferablymechanically shuttered at the desired 600 Hz by a rotating segmenteddisk contained in the light source assembly. The output of the lightsource is a pulsed beam of light. This pulsed radiation is designed tomatch the characteristics of the detectors. The microprocessor 90receives the electrical signal and effects a comparison of the thicknessinformation contained within the electrical signal with storedinformation regarding desired thickness. If the thickness is not withinthe desired range, it emits a signal to the blow-molder reject 140 whichin turn initiates a rejection signal to operate rejection apparatus 24,26 (FIG. 1) and discard that container from the conveyer. The outputthickness information from the microprocessor 90 will be delivered totouchscreen display 150 which provides an operator with informationregarding specific containers produced by particular mold and spindlecombinations. It is preferred that the values be averaged over a periodof time which may be on the order of 30 seconds to ten minutes. Inaddition or in lieu of time measurement, the average may be obtained fora fixed number of containers which may be on the order of 2 to 2500. Theoperator also obtains trend information for the blow-molder andindividual molds and spindles through the visual display unit 150. Inthe event of serious problems requiring immediate attention, visualand/or audio alarms may be provided. As indicated by the dual arrows Fand G, an operator may input certain information to the microprocessor90 to alter calibrations in order to control operation of themicroprocessor. The operator may input process limits and reject limitsinto the microprocessor 90 for each of the thickness measurement zones.The reject limits are the upper and lower thickness values that wouldtrigger the rejection of a container. The process limits are the upperand lower values for the time-averaged or number of container averagedthickness that would trigger a process alarm indicator. Also, ifdesired, hard copy or other output of the microprocessor 90 results maybe provided as by output 152 which may be a conventional printer, forexample.

The microprocessor 90 display highlights molds or spindles havingundesirable thickness—either too thick or too thin. For example, if onemold was producing containers that are too thick or too thin, theoperator would adjust mold-related parameters such as blow-pressure orblow-rate to correct the problem; or the operator might need to stop theblow-molder to replace or repair an air valve for that mold. It will beappreciated that the mold/spindle-correlated feedback provided by themicroprocessor is used to localize the problem.

Referring to FIG. 4, an algorithm flow chart showing the method of theinspection process, container tracking and combining mold and spindleinformation of the present invention will be considered. As indicated inFIG. 3, the blow-molder machine step sensor 120 will provide an outputidentified in FIG. 4 as 180 and the blow-molder mold sync sensor 122will provide an output signal 182 and the blow-molder spindle syncsensor 126 will provide a spindle sync signal 186. As shown by block190, the machine step signal 180 contains information regarding theincremental movement of the mold module, the number of molds and theincremental spindle module and the number of spindles. The mold syncsignal 182 will verify that the mold is equal to the mold offset withresetting being accomplished if necessary.

In order to adjust for the fact that microprocessor 90 may start up inthe middle of a blow-molding cycle, the microprocessor 90 preferablyemploys an algorithm that allows the microprocessor to re-synchronizewith the blow-molder 4 within one mold or spindle cycle. Themicroprocessor 90 then remains synchronized with the blow-molder 4. Thealgorithm is:

-   Machine-step event: increment mold#, if mold# is greater than number    of molds, reset to 1 increment spindle#, if spindle# is greater than    number-of-spindles, reset to 1-   Mold-sync event: Set mold# to X (mold offset as pre-configured)-   Spindle-sync event: Set spindle# to Y (spindle offset as    pre-configured)

Similarly, the spindle sync signal 186 will verify that the spindleequals the spindle offset with a reset being achieved, if necessary. Thecollective output of blocks 190, 192 and 194 is detailed informationwith respect to the current mold and spindle identity and position withrespect to the container being inspected. The sensor 130 (FIG. 3), whena container has reached the inspection level will emit signal 210 whichis combined in block 212 by associating the specific mold and signalwith this particular container and this container is tracked insynchrony with the specific mold and spindle. In the next process block214, the microprocessor will collect and process the infrared sensordata, calculate the thickness and merge the results with thecorresponding container in the tracking queue.

The output of block 214 proceeds to block 216 where, if the container isbeing rejected, it is tracked to the rejection point and a decisionregarding pass and reject has been made.

Finally, the microprocessor in block 218 updates the container thicknesstrend database and communicates the thickness information to touchscreendisplay 150 (FIG. 3). This ends the tracking of that container. It willbe appreciated that the net result is that the particular containerbeing inspected is associated with a particular mold and associatedspindle with a reject or pass decision determining whether theparticular container remains in the conveying process or is excluded bythe reject mechanism. The information also serves to update thethickness trend database as displayed in unit 150 and printed orotherwise stored or processed in output unit 152 (FIG. 3).

Referring to FIG. 5, there is shown in FIG. 5(A) the machine step timingdiagram with there being a one-for-one correspondence between themachine step pulses and containers produced by the blow-molder. The moldsync pulse shown in FIG. 5(B) indicates the start of a new cycle of themold wheel assembly and the spindle-sync pulse as shown in FIG. 5(C)shows the start of a new cycle of the spindle loop.

At the inspection station, there is a fixed phase relationship betweenthe mold sync pulse and the machine step pulse corresponding to thefirst mold. This phase information, which may be referred to as the“MoldOffset,” is determined when the system is installed into theblow-molder and then is entered into the processor. Similarly, theSpindleOffset is determined during installation and entered into theprocess.

Referring to FIG. 6, there is shown a visual display screen 240 whichcould be presented on the touchscreen display unit 150 (FIG. 3) toprovide prompt and concise feedback regarding the mold/spindlecorrelated thickness information for purposes of process control andblow-molder optimization. The process status is shown in FIG. 6. Therepresentation on the left shows a container 250 which in the form shownis a bottle having an exteriorly threaded neck. The wall thickness hasbeen measured at vertically spaced levels 252, 254, 256. Each band 252,254, 256 will contain a numerical indication of the average wallthickness. These indicated numbers show the process-wide averagethickness at these measurement locations averaged over a certainselected period of time which may be on the order of 30 seconds to 10minutes or could be an average of a number of containers from about 2 to2500.

Referring still to FIG. 6, it is noted by way of example that band 252is subdivided into a plurality of units 255, 257, 259, 260, 262, each ofwhich may be presented in a distinctive color different from nextadjacent subportions of band 252 for ease of visual review. By way ofexample, the numbers underlying band 252 present a scale of thickness ininches taken to four decimal points. Overlying the band 252 appears thenumber 0.2088 with an inverted triangle pointing to a portion of band252. This number represents an average wall thickness at that locationof the bottle based on, for example, a period of time or a number ofcontainers measured. One seeing the computer screen 240, therefore, canquickly ascertain not only quantitatively what the average thicknessmeasurement has been, but also visually in terms of the position on thescale. Similar numerical scales and reading information would preferablybe contained on bands 254, 256.

On the right in FIG. 6 is a graphic representation of the mold wheelassembly 280 having each mold represented by a circle and containinginformation regarding the related container thickness. In the center ofthe mold circle, there is a grid 300 showing container thickness statusfor a number of spindles. As the number of spindles can be quite large,the display shows a pareto-optimized list of problem spindles with theidentity of the worst spindle problems being identified by a spindlenumber or other identifier.

With respect to the molds, it is noted that some indication regardingthickness may be provided by the use of different colors. For example,as shown, the number 290 points to a mold which has a whiterepresentation, as does 292. The remaining molds are shown in black. Asuitable scale may be provided so that the white indicates a thicknessabove or below control limits and the black indicates a thickness withinlimits . As these circles may contain numbers (not shown) identifying aparticular mold, this will enable an operator to obtain a visualindication regarding the average thickness as related to control limitsor reject limits for that mold. With regard to spindle representing grid300, as there are more spindles than shown in the grid, this embodimentwould employ the worst of the spindles in respect of containers whichhave been inspected and having the greatest departure from desired wallthickness. By way of example, the top row of squares identifiedrespectively by reference numbers 304, 306, 308, 310, 312, 314 areidentified respectively and related to spindles 1, 3, 12, 20, 21, 23. Asis true with the molds, these grid representations would preferably havecolor coding indicating as to each spindle in the grouping, the degreeof departure from the control limits or reject limits or, in the eventthat it is within limits, a color indicating that category. It will beappreciated that while the drawings show color representations for themolds as being black or white, and no color distinctions are provided inthe illustrated grid 300, two or more colors may be employed inrespective circles and blocks to indicate various thickness averages asrelated to the desired limits.

If desired, additional information may be provided on the screen 240.For example, if the average is based upon a time of 3 minutes, a legendto that effect may be provided. Similarly, if the average thickness isbased upon the last 250 bottles, a legend to this effect may beprovided. Also, information regarding the total number of rejects andthe percentage of rejects may be provided. Numerical indications of thenumber of rejects coming from each of the molds and spindles may also beprovided. The color codes or symbols such as “+” or “−” may be employedto identify whether the departure from desired control limits or rejectlimits are above or below such limits.

Where two distinct wavelengths of infrared radiation are used, a firstwill be at a wavelength which is readily absorbed by the plasticmaterial of the container and the other wavelength will be only slightlyabsorbed. A further possibility is that the containers may be filledwith condensed water vapor at the end of the blow-molding process. Ifthat is sufficiently dense, the internal fog formed in the container mayscatter light away from the sensors and interfere with measurement. Ifdesired, a third infrared wavelength which is not at an absorption bandwith respect to the plastic material can be used in order to calculate acorrection factor to enhance the accuracy of the thickness measurementby correcting for optical scattering caused by the fog.

It will be appreciated that the present invention has provided animproved automated system for wall thickness determination in a plasticcontainer which, as a result of sensors operatively associated with theblow-molder, provides detailed information so as to correlate wallthickness of a given container with the mold and spindle at which it ismade. The microprocessor processes data regarding the thicknessmeasurement and outputs the same to a unit which may visually displayand/or to another unit which may provide hard copy of the averagethickness readings which may also be a thickness reading achieved over aperiod of time such as about 30 seconds to 10 minutes or a number ofcontainers which may be about 2 to 2500.

1. A method of inspecting a blow-molded plastic container for acontainer attribute determined from light absorption comprisingproviding a plastic container blow-molder having a plurality of moldsand a plurality of spindles, inspecting said container by impinginglight thereon from the exterior thereof and detecting the portion ofsaid light that passes through two walls of said container, convertingsaid detected light into corresponding electrical signals which aredelivered to a microprocessor, comparing in said microprocessor saidelectrical signals with stored data regarding desired said containerattribute and emitting output information regarding said containerattribute, and delivering to said microprocessor signals received fromsensors associated with said blow-molder relating to said mold and saidspindle involved in making the container being inspected.
 2. The methodof claim 1, including delivering to said microprocessor signals from asensor associated with said blow molder for determining the position ofsaid molds and said spindles.
 3. The method of claim 1, includinginspecting a plurality of vertically spaced portions of said containersubstantially simultaneously.
 4. The method of claim 3, including saidmicroprocessor providing output information for each said verticallydisposed portion.
 5. The method of claim 4, including employing aplurality of detectors in effecting said detecting, and employing aplurality of infrared light sources each operatively associated with asaid detector.
 6. The method of claim 1, including automaticallyrejecting any container which does not pass said inspection byseparating the same from adjacent non-rejected containers.
 7. The methodof claim 1, including sensing within said blow-molder the position ofsaid molds.
 8. The method of claim 7, including delivering said sensorobtained mold position information to said microprocessor.
 9. The methodof claim 1, including said sensors associated with said blow-molderbeing disposed within said blow-molder.
 10. The method of claim 1,including employing said output information to adjust operation of saidblow-molder when undesired container attribute variations occur.
 11. Themethod of claim 1, including employing said output information toinitiate an alarm when predetermined conditions exist.
 12. The method ofclaim 1 wherein said container attribute includes container wallthickness.
 13. The method of claim 1, including employing infrared lightas said light.
 14. The method of claim 13, including said microprocessoroutput information having identification and location of said mold andidentification of said spindle employed in making said container, andemploying two distinct infrared wavelengths in said inspection method.15. The method of claim 13, including said container attribute includescontainer wall thickness.
 16. A method of inspecting blow-molded plasticcontainers for a container attribute to be determined from lightabsorption comprising providing a plastic container blow-molder having aplurality of molds and plurality of spindles, inspecting said containerby impinging light thereon and detecting the portion of said light thatpasses through said container, converting said detected light intocorresponding electrical signals which are delivered to amicroprocessor, comparing in said microprocessor said electrical signalswith stored data regarding said desired container attribute and emittingoutput information regarding said container, delivering to saidmicroprocessor signals received from sensors associated with saidblow-molder relating to said mold and said spindle involved in makingthe container being inspected, and employing two distinct wavelengths oflight in said inspection method.
 17. The method of claim 16 wherein saidcontainer attribute includes container wall thickness.
 18. The method ofclaim 16, including said source of light being a source of infraredlight.
 19. The method of claim 16, including employing said outputinformation to adjust operation of said blow-molder when undesiredcontainer attribute variations occur.
 20. A method of inspectingblow-molded plastic containers comprising providing a plastic containerblow-molder having a plurality of molds and a plurality of spindles,inspecting said container by impinging light thereon and detecting theportion of said light that passes through container, converting saiddetected light into corresponding electrical signals which are deliveredto a microprocessor, comparing in said microprocessor said electricalsignals with stored data regarding desired said container attribute andemitting output information regarding said container attribute,delivering to said microprocessor signals received from sensorsassociated with said blow-molder relating to said mold and said spindleinvolved in making the container being inspected, inspecting a pluralityof vertically spaced portions of said container substantiallysimultaneously, said microprocessor providing output information foreach said vertically disposed portion, and visually displaying at leasta portion of said microprocessor emitted output information.
 21. Themethod of claim 20, including said output information associatingcontainer attribute information with identification of the mold and thespindle involved in the manufacture of said container.
 22. The method ofclaim 21, including including in said output information an attributeaveraged for a time period.
 23. The method of claim 22, includingupdating said output information after each inspection of a saidcontainer.
 24. The method of claim 22, including said time period beingabout 30 seconds to 10 minutes.
 25. The method of claim 21, includingincluding in said output information an attribute averaged for a numberof containers.
 26. The method of claim 25, including said number ofcontainers being about 2 to
 2500. 27. The method of claim 20, includingproviding a reject station for physically removing rejected containers,and effecting said inspection after said container emerges from saidblow-molder but prior to the container's reaching said rejectionstation.
 28. The method of claim 20, including effecting said inspectionon-line.
 29. The method of claim 20, including prior to initiating aninspection cycle confirming the presence of a container at the desiredinspection position.
 30. The method of claim 20 wherein said containerattribute includes container wall thickness.
 31. The method of claim 20,including said source of light being a source of infrared light.
 32. Themethod of claim 20, including employing said output information toadjust operation of said blow-molder when undesired container attributevariations occur.
 33. Apparatus for inspecting a container attributedetermined from light absorption of blow-molded plastic containerscomprising a blow-molder having a plurality of molds and a plurality ofspindles, at least one source of light for impinging said light on saidcontainer from the exterior thereof, at least one detector for receivinglight passing through two walls of said container and converting thesame into corresponding electrical signals, a microprocessor forreceiving said electrical signals and determining the containerattribute is within desired limits and emitting output information, andblow-molder sensors associated with said blow-molder to identify saidmolds and spindles and provide input to said microprocessor from whichit can associate said container output information with the mold andspindle which made said container.
 34. The apparatus of claim 33,including said blow-molder sensors providing information regarding thepositions of said molds and delivering a position signal to saidmicroprocessor, and said source of light being structured to emit lightof two different wavelengths.
 35. The apparatus of claim 34, including aplurality of said light sources and light detectors arranged to permitinspection of said container attribute at a plurality of verticallyspaced locations, a visual display unit for receiving output informationfrom said microprocessor and displaying the same, and said visualdisplay unit providing separate information for each said mold and eachsaid spindle.
 36. The apparatus of claim 34, including said source oflight being a source of infrared light.
 37. The apparatus of claim 33,including a container position sensor for confirming that a container ispresent at the desired inspection position and emitting a signal to saidmicroprocessor.
 38. The apparatus of claim 33, including saidmicroprocessor output information including average attribute value-overa predetermined time period.
 39. The apparatus of claim 33, including avisual display unit for receiving said-output information from saidmicroprocessor and displaying the same.
 40. The apparatus of claim 39,including said visual display unit providing separate information foreach said mold and each said spindle.
 41. The apparatus of claim 39,including said visual display unit displaying information regardingaverage attribute value over a period of time.
 42. The apparatus ofclaim 39 including said microprocessor being structured to update saidoutput information after each inspection of a said container.
 43. Theapparatus of claim 33 including reject apparatus for removing acontainer if said microprocessor determines that the container attributeis not within a desired range.
 44. The apparatus of claim 43, includingsaid microprocessor being structured to effect an adjustment of saidblow-molder responsive to the existence of a rejected container.
 45. Theapparatus of claim 44, including effecting said adjustment to aparameter selected from the group consisting of blow pressure and blowrate.
 46. The apparatus of claim 33 including said container attributeincludes container wall thickness.
 47. The apparatus of claim 33,wherein said microprocessor determines an amount of said light absorbedby said container based on said electrical signals and determineswhether the container attribute is within desired limits based on saidamount of said light absorbed by said container.
 48. Apparatus forinspecting blow-molded plastic containers for a container attributedetermined from light absorption comprising a blow-molder having aplurality of molds and a plurality of spindles, at least one source oflight for impinging said light on said container, at least one detectorfor receiving light passing through said container and converting thesame into corresponding electrical signals, a microprocessor forreceiving said electrical signals and determining whether the containerattribute values are within desired limits and emitting outputinformation, blow-molder sensors associated with said blow-molder toidentify said molds and spindles and provide input to saidmicroprocessor from which it can associate said output information withthe mold and spindle which made said container, and said source of lightemitting light of two different wavelengths.
 49. The apparatus of claim48, including said apparatus being positioned for on-line inspection ofsaid containers.
 50. The apparatus of claim 48, including averaging saidattribute values for a time period of about 30 seconds to 10 minutes.51. The apparatus of claim 48, including said microprocessor outputinformation including average attribute values for a number ofcontainers.
 52. The apparatus of claim 51, including said number ofcontainers being about 2 to
 2500. 53. The apparatus of claim 48,including said microprocessor output information being an averageattribute value, said apparatus having a visual display unit, and saidvisual display unit displaying said average attribute value as relatedto specific said molds and spindles.
 54. The apparatus of claim 53,including said microprocessor average attribute value being for aspecific period of time.
 55. The apparatus of claim 53, including saidmicroprocessor average attribute values being for a specific number ofcontainers.
 56. The apparatus of claim 48 including said containerattribute includes container wall thickness.
 57. The apparatus of claim48 including said source of infrared light emitting a first saidwavelength which corresponds to an absorption band of said plastic andemitting a second said wavelength which is different from said firstsaid wavelength which is only slightly absorbed by said plastic.
 58. Theapparatus of claim 48, including said source of light being a source ofinfrared light.
 59. The apparatus of claim 48, wherein saidmicroprocessor determines an amount of said light absorbed by saidcontainer based on said electrical signals and determines whether thecontainer attribute is within desired limits based on said amount ofsaid light absorbed by said container.
 60. Apparatus for inspecting fora container attribute of a plastic container formed by a blow-molderwhich has a plurality of molds and a plurality of spindles and isoperably associated with blow-molder sensors comprising at least onesource of light for impinging said light on said container from theexterior thereof, at least one detector for receiving light passingthrough two walls of said container and converting the same intocorresponding electrical signals, a microprocessor for receiving saidelectrical signals and determining whether the container attribute iswithin desired limits and emitting output information related to saidelectrical signals, and said microprocessor structured to receive inputfrom said blow-molder sensors from which it can associate said containeroutput information with the mold and spindle which made said container.61. The apparatus of claim 60, including said source of light being asource of infrared light.
 62. The apparatus of claim 61, including saidblow-molder sensors providing information regarding the positions ofsaid molds and delivering a position signal to said microprocessor, andsaid source of infrared light being structured to emit infrared light oftwo different wavelengths.
 63. The apparatus of claim 62, including saidmicroprocessor output information including average attribute value overa predetermined time period.
 64. The apparatus of claim 62, including aplurality of said infrared light sensors and infrared detectors topermit inspection of said container attribute at a plurality ofvertically spaced locations, a visual display unit for receiving outputinformation from said microprocessor and displaying the same, and saidvisual display unit providing separate information for each said moldand each said spindle.
 65. The apparatus of claim 60, including acontainer position sensor for confirming that a container is present atthe desired inspection position and emitting a signal to saidmicroprocessor.
 66. The apparatus of claim 60, including a visualdisplay unit for receiving said output information from saidmicroprocessor and displaying the same.
 67. The apparatus of claim 66,including said visual display unit providing separate information foreach said mold and each said spindle.
 68. The apparatus of claim 66,including said visual display unit displaying information regardingaverage attribute value over a period of time.
 69. The apparatus ofclaim 66, including said microprocessor being structured to update saidoutput information after each inspection of a said container.
 70. Theapparatus of claim 60, wherein said microprocessor determines an amountof said light absorbed by said container based on said electricalsignals and determines whether the container attribute is within desiredlimits based on said amount of said light absorbed by said container.71. The apparatus of claim 60, including reject apparatus for removing acontainer if said microprocessor determines that the wall thickness isnot within a desired range.
 72. The apparatus of claim 71, includingsaid microprocessor being structured to effect an adjustment of saidblow-molder responsive to the existence of a rejected container.
 73. Theapparatus of claim 72, including said microprocessor being structured toeffect an adjustment to a parameter selected from the group consistingof blow pressure and blow rate.
 74. The apparatus of claim 60 whereinsaid attribute includes wall thickness.
 75. Apparatus for inspecting fora container attribute of a plastic container formed by a blow-molderwhich has a plurality of molds and a plurality of spindles and isoperatively associated with blow-molder sensors comprising at least onesource of light for impinging said light on said container, at least onedetector for receiving light passing through said container andconverting the same into corresponding electrical signals, amicroprocessor for receiving said electrical signals and determiningwhether the container attribute values are within desired limits andemitting output information related to said electrical signals, saidmicroprocessor structured to receive input from said blow-molder sensorsfrom which it can associate said output information with the mold andspindle which made said container, and said source of light emittinglight of two different wavelengths.
 76. The apparatus of claim 75,including said source of light being a source of infrared light.
 77. Theapparatus of claim 76, including said apparatus being positioned foron-line inspection of said containers.
 78. The apparatus of claim 75,including averaging said attribute values for a time period of about 30seconds to 10 minutes.
 79. The apparatus of claim 75, including saidmicroprocessor output information including average attribute values fora number of containers.
 80. The apparatus of claim 79, including saidnumber of containers being about 2 to
 2500. 81. The apparatus of claim75, including said microprocessor output information being an averageattribute value, said apparatus having a visual display unit, and saidvisual display unit displaying said average attribute value as relatedto specific said molds and spindles.
 82. The apparatus of claim 81,including said microprocessor average attribute value being for aspecific period of time.
 83. The apparatus of claim 81, including saidmicroprocessor average attribute values being for a specific number ofcontainers.
 84. The apparatus of claim 75 wherein said attributeincludes wall thickness.
 85. The apparatus of claim 84, including rejectapparatus for removing a container if said microprocessor determinesthat the wall thickness is not within a desired range.
 86. The method ofclaim 75, including employing said microprocessor to effect anadjustment of said blow-molder after rejection of a said container. 87.The method of claim 86, including effecting said adjustment to aparameter selected from the group consisting of blow pressure and blowrate.
 88. The apparatus of claim 75, including reject apparatus forremoving a container if said microprocessor determines that saidcontainer attribute is not within a desired range.
 89. The apparatus ofclaim 88, including said microprocessor being structured to effect anadjustment of said blow-molder responsive to the existence of a rejectedcontainer.
 90. The apparatus of claim 75, including reject apparatus forremoving a container if said microprocessor determines that the saidcontainer attribute is not within a desired range.
 91. The apparatus ofclaim 90, including said microprocessor being structured to effect anadjustment of said blow-molder responsive to the existence of a rejectedcontainer.
 92. The apparatus of claim 75, wherein said microprocessordetermines an amount of said light absorbed by said container based onsaid electrical signals and determines whether the container attributeis within desired limits based on said amount of said light absorbed bysaid container.